Lan adapter

ABSTRACT

This LAN adapter is for connecting an information appliance to a LAN, and writes the default IP address stored in ROM through nonvolatile memory to working memory as the IP address of the LAN adapter only when it is determined by a connection detector for determining if the LAN adapter is connected to the LAN that there is not another device on the LAN connected to the LAN adapter. If it is determined that there is a device on the LAN connected to the LAN adapter, the content of the nonvolatile memory is written to the working memory.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a LAN adapter for connecting aninformation appliance to an Ethernet (R) or other local area network(LAN).

2. Description of the Background Art

Even residential users can now access the Internet using a number ofdifferent broadband network connections, including xDSL, optical fiber,and cable. This infrastructure has made it possible to control AVequipment, lighting, and heating and cooling systems in the home overthe Internet (referred to below as an IP communications network). A LANadapter is needed to connect these devices (information appliances) toan IP communications network.

It is also necessary to set required communications parameters in orderto connect this LAN adapter to the network. These communicationparameters are parameters required to connect the LAN adapter to theLAN, and include the user ID, password, IP (Internet protocol) address,whether the IP address is automatically assigned using dynamic hostconfiguration protocol (DHCP) (referred to below as the DHCP setting),and the type of information appliance connected by the LAN adapter.

The communication parameters are generally set in the LAN adapter byusing a personal computer connected to the same LAN as the LAN adapterto change the parameters. This requires specifying the known local IPaddress of the LAN adapter. Using a global IP address instead of a localIP address to set the communication parameters is a security riskbecause the communication parameters can be changed from a terminal noton the LAN. The communication parameters are therefore normally setusing only the. local IP address of the device on the local areanetwork.

A conventional LAN adapter is described further below with reference toFIG. 11 to FIG. 15.

FIG. 11 is a schematic block diagram of a conventional LAN adapter 200connected to a network 205. This LAN adapter 200 is connected to aninformation appliance 201 such as a VCR or television, and is connectedthrough a LAN port to a LAN cable in the LAN. Included in the LAN shownin FIG. 11 are an ADSL modem 204, router 203, information processor 202,LAN adapter 200, and information appliance 201. The informationprocessor 202 is typically a personal computer. The LAN is connected tothe Internet or other wide area network 205 via a telephone line, forexample, and can communicate via the network 205 with a personalcomputer, a portable data terminal, or other external device 206.

The information appliance 201 can be accessed and operated by aninformation processor 202 on the LAN through the LAN adapter 200 underpredefined conditions. It can also be accessed and operated from anexternal device 206 connected to the network 205 to which the LAN isconnected by means of the router 203 and network 205. Conversely, theinformation appliance 201 can also access and operate the informationprocessor 202 on the LAN by way of the LAN adapter 200 under predefinedconditions, and can access and operate an external device 206 not on theLAN by way of network 205 and router 203.

FIG. 12 is a block diagram showing the configuration of a conventionalLAN adapter 200. This LAN adapter 200 connects to the LAN eitherwirelessly or by a wired connection through LAN port 51. The LAN adapter200 also has working memory 55 and nonvolatile memory 56. The workingmemory 55 stores LAN adapter 200 settings and information about thesettings of the information processor 202 and router 203 on the LAN. Thenonvolatile memory 56 is typically flash memory, which is readable andwritable. The IP address written to working memory 55 is used as the IPaddress of the LAN adapter 200 on the LAN.

The LAN adapter 200 also has a management unit 53, controller 54, resetbutton 59, reset unit 60, power supply 61, and input/output (I/O) unit62. The management unit 53 enables communication over the LAN, and isthe management means for managing the settings of the LAN adapter 200,and information relating to the settings of the information processor202 and router 203, external devices connected to the LAN. Thecontroller 54 is a control means for controlling the management unit 53,working memory 55, and nonvolatile memory 56, and controllingcommunication with the information appliance 201. When the reset button59 is pressed, the reset unit 60 issues a signal for clearing theworking memory 55. The power supply 61 is the power supply for the LANadapter 200, and operates the reset unit 60 by turning the power supplyoff and then on again. The I/O unit 62 is the input/output meansconnected to the information appliance 201.

FIG. 13 is a block diagram showing a connection for setting thecommunication parameters in order to connect a LAN adapter 200 to theLAN. This is generally done by connecting the LAN adapter 200 with acommunication parameter setting device 207 using a LAN cable to set thecommunication parameters. The communication parameter setting device 207in this case is a personal computer, cell phone, or other deviceenabling electronic data processing.

FIG. 14 is a flow chart showing the operation for setting thecommunication parameters of the LAN adapter 200 (referred to as thecommunication parameter configuration below) after the LAN adapter 200and communication parameter setting device 207 are connected via a LANcable as shown in FIG. 13. This method is used to configure thecommunication parameters for connecting a LAN adapter 200 to the LANwhen the user knows the IP address stored in the nonvolatile memory 56of the LAN adapter 200.

(a) The reset unit 60 sends a command to the controller 54 for clearingthe working memory 55 when the user presses the reset button 59, forexample (S51: reset step).

(b) The controller 54 reads and writes the communication parametersstored in nonvolatile memory 56 to working memory 55 (S52: workingmemory initialization step).

(c) Communication between the LAN adapter 200 and communicationparameter setting device 207 is enabled by setting the IP address of theLAN adapter 200 using the communication parameter setting device 207(S53: connection configuration step).

(d) The communication parameter setting device 207 is then used to writeand set the communication parameters in nonvolatile memory 56 of LANadapter 200 (S54: communication parameter configuration step).

FIG. 15 is a flow chart for rewriting the IP address of the LAN adapter200 from an information processor 202, i.e., a device on the LAN, whenthe conventional LAN adapter 200 is connected to the LAN as shown inFIG. 11. This method enables using the LAN adapter 200 on the LAN whenthe appropriate communication parameters are stored in nonvolatilememory 56 and normal communication is possible on the LAN shown in FIG.11.

(a) The user presses the reset button 59 so that the reset unit 60 sendsa reset command to the controller 54. (S51: reset step)

(b) The controller 54 reads and writes the communication parametersstored in nonvolatile memory 56 to working memory 55 (S52: workingmemory initialization step).

(c) The controller 54 detects the static IP address signal from theinformation processor 202 (S55: static IP address detection step).

(d) When the controller 54 detects the static IP address signal in thestatic IP address detection step S55, it writes the static IP address toworking memory 55 and nonvolatile memory 56 (S56: static IP addressstorage step).

(e) The controller 54 detects a signal indicating whether DHCP should beused (DHCP setup signal) (S57: DHCP setup signal detection step).

(f) If the DHCP setup signal is detected in the DHCP setup signaldetection step S57, the DHCP setup parameter is set in working memory 55and nonvolatile memory 56 to use the DHCP function of the router 203(S58: dynamic IP configuration step).

By forming a loop returning to before the static IP address detectionstep S55 after the static IP address storage step S56, DHCP setup signaldetection step S57, or dynamic IP configuration step S58, the systemwaits for the static IP address signal and DHCP address signal. The LANadapter 200 can then be used on the LAN.

SUMMARY OF THE INVENTION

A problem with the configuration described above is that there is nodisplay unit for displaying the IP address stored to working memory 55and nonvolatile memory 56. This means that if the user of theinformation processor 202 does not know the IP address stored to workingmemory 55 or nonvolatile memory 56, there is no way for the user of theinformation processor 202 to learn the IP address. The problem here isthat it may not be possible to restore access to the LAN adapter 200from another LAN device.

Furthermore, because the IP address can only be set from an externaldevice connected through LAN port 51, it would be sufficient to resetthe IP address from such an external device to enable use on the LAN.However, in order to operate the LAN adapter from an external device,the LAN adapter 200 must first be accessed from the external device andthis requires knowing the IP address of the LAN adapter 200. If the.user does not know the IP address of the LAN adapter 200 in this casethe LAN adapter 200 cannot be accessed and the IP address thereforecannot be reset. If the user sets a static IP address as the IP addressof each device on the LAN, it is difficult for the user to know the IPaddress each time an address is changed and the user of the informationprocessor 202 may not know the IP address stored to the working memory55 and nonvolatile memory 56 of the LAN adapter 200.

Furthermore, when the LAN adapter 200 is set to use DHCP, the IP addressis automatically assigned by the router 203, and external devices canonly access the LAN adapter 200 through the router 203. However, if theDHCP function of the router 203 is not operating normally, access to theLAN adapter 200 cannot be restored because the IP address of the LANadapter 200 cannot be set directly from the external device.

The present invention is therefore directed to providing a LAN adapterfor restoring a LAN connection when desired by the user even if the IPaddress of the LAN adapter is not known.

A LAN adapter according to the present invention for connecting aninformation appliance to a local area network comprises a first storagedevice which stores the currently recognized IP address of the LANadapter on a LAN; a second storage device which stores a default IPaddress for the LAN adapter; a controller which controlling the firststorage device and second storage device; an IP address initializationcontroller which controls initializing the IP address of the LANadapter; a connection detector which detects whether there is a deviceon the LAN connected to the LAN adapter in response to a command fromthe IP address initialization controller; and an IP addressinitialization means which initializes the IP address of the LAN adapteraccording to the connection detected by the connection detector.

When the connection detector determines that there is no device on theLAN connected to the LAN adapter, the controller writes the default IPaddress stored in the second storage device to the first storage deviceas the IP address of the LAN adapter.

The LAN adapter thus comprised can therefore restore a connection on theLAN even when the user does not know the IP address of the LAN adapter.

BRIEF DESCRIPTION OF THE DRAWINGS

The object, features, and benefits of the present invention will beapparent from the preferred embodiments described below in conjunctionwith the accompanying figures:

FIG. 1 is a block diagram of the connection of a LAN adapter accordingto a first embodiment of the present invention to a LAN;

FIG. 2 is a block diagram of the configuration of an informationappliance according to a first embodiment of the present invention whenconnected to a LAN;

FIG. 3 is a block diagram of the configuration of a LAN adapteraccording to a first embodiment of the present invention;

FIG. 4 is a block diagram of the connection enabling setting thecommunication parameters of a LAN adapter according to a firstembodiment of the present invention;

FIG. 5 is a flow chart of the operation for setting the communicationparameters of a LAN adapter according to a first embodiment of thepresent invention;

FIG. 6 is a flow chart of initializing the IP address of a LAN adapteraccording to a first embodiment of the present invention;

FIG. 7 is a flow chart of operation of the reset unit of a LAN adapteraccording to a first embodiment of the present invention;

FIG. 8 is a flow chart of a method for setting the IP address when a LANadapter according to a first embodiment of the present invention isconnected to a LAN;

FIG. 9 is a block diagram of the configuration of a LAN adapteraccording to a second embodiment of the present invention;

FIG. 10 is a flow chart of initializing the IP address of a LAN adapteraccording to a second embodiment of the present invention;

FIG. 11 is a block diagram of the connection of a LAN adapter accordingto the prior art when connected to a LAN;

FIG. 12 is a block diagram of the configuration of a conventional LANadapter;

FIG. 13 is a block diagram of the connection for setting thecommunication parameters of a conventional LAN adapter;

FIG. 14 is a flow chart of setting the communication parameters of aconventional LAN adapter; and

FIG. 15 is a flow chart of the operation of a conventional LAN adapter.

DETAILED DESCRIPTION OF THE INVENTION

A LAN adapter according to a preferred embodiment of the presentinvention is described below with reference to the accompanying figures.It should be noted that functionally like parts are identified by thesame reference numerals in the figures.

(Embodiment 1)

FIG. 1 is a block diagram of a LAN adapter according to a firstembodiment of the present invention connected to a network. This LANadapter 100 is connected to a video recorder, camera, television, orother information appliance 101, and is connected through a LAN port toa LAN cable on the local area network. Of the devices shown in thefigure, the ADSL modem 104, router 103, personal computer or otherinformation processor 102, LAN adapter 100, and information appliance101 form a LAN. This LAN is further connected to a network 105 such asthe Internet by way of a telephone line, and is also connected throughthe network 105 to a personal computer, cell phone, portable dataterminal, or other external device 106. The information appliance 101 isaccessible and operable by an information processor 102 on the LANthrough the LAN adapter 100 under specific conditions. The informationappliance 101 can also be accessed and operated through the network 105and router 103 from an external device 106 connected to a network 105other than the LAN. Conversely, the information appliance 101 can alsoaccess and operate an information processor 102 on the LAN through theLAN adapter 100 under specific conditions. Furthermore, the informationappliance 101 can also access and operate a external device 106 that isnot on the LAN through the network 105 and router 103.

FIG. 2 is a block diagram of how an information appliance 101 containinga LAN adapter 100 connects to the network 105. By incorporating the LANadapter 100 inside the information appliance 101, the LAN adapter 100 iseasier to handle than when it is separate.

FIG. 3 is a block diagram of the configuration of a LAN adapteraccording to a first embodiment of the present invention. This LANadapter 100 is connected wirelessly or by wire to a LAN through LAN port1, and has working memory 5, nonvolatile memory 6, and ROM (read-onlymemory) 7. The working memory 5 stores information about the settings ofthe LAN adapter 100 and the settings of the router 103 and informationprocessor 102 connected to the LAN. The nonvolatile memory 6 isreadable/writable flash memory, for example. ROM 7 stores a predefineddefault IP address for the LAN adapter 100, and is a ROM device used asa second storage device that can only be read and cannot be written.

LAN adapter 100 also has management unit 3, controller 4, reset button9, reset unit 10, power supply 11, and I/O unit 12. The management unit3 enables LAN communications, and is the management means for managinginformation relating to the settings of the LAN adapter and the settingsof the router 103 and information processor 102 as external devicesconnected over the LAN.

The controller 4 controls the management unit 3, working memory 5,nonvolatile memory 6, and ROM 7, and controls communication with theinformation appliance 101.

When the reset button 9 is depressed, reset unit 10 issues a command forclearing the working memory 5.

The power supply 11 is the power supply unit of the LAN adapter 100, andoperates the reset unit 10 by turning the power on again after turningit off.

The I/O unit 12 is the input/output means connected to the informationappliance 101.

The LAN adapter 100 also has an IP address initialization button 13,connection detector 14, and IP address initialization unit 15. When theIP address initialization button 13 is depressed, the connectiondetector 14 determines whether there is another device on the LANconnected to the LAN adapter 100. If it is determined that there is nodevice on the LAN connected to the LAN adapter 100, the IP addressinitialization unit 15 issues an IP address initialization command forsetting the IP address of the LAN adapter 100 to the default IP addressstored in ROM 7. More specifically, working memory 5 is cleared and thedefault IP address stored in ROM 7 is written through nonvolatile memory6 to working memory 5.

However, if it is determined that another device on the LAN is connectedto the LAN adapter 100, working memory 5 is cleared and the content ofnonvolatile memory 6 is written to working memory 5. Because the IPaddress currently recognized as the address of the LAN adapter on theLAN is stored to nonvolatile memory 6 in this case, the current IPaddress is written to the working memory 5. The IP address is thereforenot initialized in this case. By thus confirming whether a device isconnected to the LAN adapter over the LAN, interrupted connectionscaused by the IP address of the LAN adapter 100 changing when anotherdevice has accessed the LAN adapter 100 can be prevented.

FIG. 4 is a block diagram of a connection for setting the communicationparameters, for example, when connecting this LAN adapter 100 to theLAN. This is generally done by connecting the LAN adapter 100 andcommunication parameter setting device 107 by a LAN cable and thensetting the communication parameters for the LAN adapter 100. Thecommunication parameter setting device 107 in this case is a personalcomputer, cell phone, or other device enabling electronic dataprocessing.

FIG. 5 is a flow chart of the operation for setting the communicationparameters of the LAN adapter 100 (referred to as the communicationparameter configuration below) after the LAN adapter 100 andcommunication parameter setting device 107 are connected via a LAN cableas shown in FIG. 4. This method is used to configure the communicationparameters for connecting a LAN adapter 100 to the LAN when the userknows the IP address stored in the nonvolatile memory 6 of the LANadapter 100.

(a) The reset unit 10 sends a command to the controller 4 for clearingthe working memory 5 when the user presses the reset button 9, forexample. (S1: reset step)

(b) The controller 4 reads and writes the communication parametersstored in nonvolatile memory 6 to working memory 5 (S2: working memoryinitialization step).

(c) Communication between the LAN adapter 100 and communicationparameter setting device.107 is enabled by setting the IP address of theLAN adapter 100 using the communication parameter setting device 107(S3: connection configuration step).

(d) The communication parameter setting device 107 is then used to writeand set the communication parameters in nonvolatile memory 6 of LANadapter 100 (S4: communication parameter configuration step).

FIG. 6 is a flow chart of an operation for setting the IP address of theLAN adapter 100 to the default IP address. This method is used to setthe communication parameters when the user does not know the current IPaddress of the LAN adapter 100 stored in nonvolatile memory 6.

(a) When the user presses the IP address initialization button 13, thecontroller 4 detects that the button 13 was pressed (S5: IP addressinitialization button depression step).

(b) The connection detector 14 detects whether there is a device on theLAN connected to the LAN adapter 100 (S6: connection detection step).

(c) If the connection detector 14 determines that there is no device onthe LAN connected to the LAN adapter 100 (yes), working memory 5 iscleared by the controller 4 (S7: working memory initialization step).

(d) After the working memory 5 is initialized, the default IP addressstored in ROM 7 is written to nonvolatile memory 6, and the content ofnonvolatile memory 6 is then written to working memory 5 (S8: default IPaddress writing step). This “default IP address” means the IP addressstored in ROM 7. Writing this default IP address to working memory 5enables the known IP address of the LAN adapter 100 to be used whensetting the communication parameters. It should be noted that the firststorage device comprises working memory 5 and nonvolatile memory 6.

(e) If the connection detector 14 determines that there is a device onthe LAN connected to LAN adapter 100 (no), working memory 5 is clearedby controller 4 (S9: working memory initialization step).

(f) After initializing the working memory 5, the content of nonvolatilememory 6 is written to working memory 5 (S10: write content ofnonvolatile memory step). The IP address of the LAN adapter 100 is notinitialized in this case. If the IP address is changed when there isalready a device on the LAN connected to the LAN adapter 100, the LANadapter 100 will no longer be recognized by that device. This problemcan be prevented, however, by writing the current IP address whenanother device is known to be connected to the LAN adapter 100.

The above method for detecting a connection is described next. If thenetwork connection is, for example, a 10BASE-T connection conforming toIEEE 802.3, devices connected over the network are found by checking atthe physical layer (or the physical layer IC device level). This makesit possible to know that a connected device is not on the network. Itwill be obvious that the connection detection method shall not be solimited. The connection detection method will vary according to thenetwork connection type, such as a wired LAN or wireless LAN, and thedetection method will vary according to the type of network connectionused.

FIG. 7 is a flow chart of operation when the reset button 9 is pressedor when the power supply 11 is turned on from an off state.

(a) The reset unit 10 detects whether the reset button 9 was pressed orwhether the supply of power to the power supply 11 started (S11: resetstep).

(b) The reset unit 10 outputs a reset signal instructing the controller4 to clear working memory 5, and the controller 4 thus clears workingmemory 5 s (S12: working memory initialization step). The reset meanscomprises the reset unit 10, reset button 9, and power supply 11.

(c) The reset signal from the reset unit 10 also causes the controller 4to write the content of nonvolatile memory 6 to working memory 5 (S13:write content of nonvolatile memory step). Note that the currentlyrecognized IP address of the LAN adapter 100 on the LAN is stored tononvolatile memory 6. The IP address written to the working memory 5 isthe IP address of the LAN adapter 100 on the LAN.

FIG. 8 is a flow chart of the operation for rewriting the IP address ofthe LAN adapter 100 from the information processor 102, a device on theLAN, when the LAN adapter 100 is connected to the LAN as shown inFIG. 1. This method enables the LAN adapter to be used on the LAN whenthe communication parameters stored to nonvolatile memory 6 areappropriate and normal communication is possible on the LAN configuredas shown in FIG. 1.

(a) The user operates the reset button 9 so that a reset signal isoutput from the reset unit 10 to the controller 4 (S14: reset step).

(b) The controller 4 reads and writes the communication parametersstored in nonvolatile memory 6 to working memory 5 (S15: working memoryinitialization step).

(c) The controller 4 detects the static IP address signal from theinformation processor 102 (S16: static IP address detection step).

(d) If the controller 4 detects the static IP address signal in thestatic IP address detection step S16, it writes the static IP address toworking memory 5 and nonvolatile memory 6 (S17: static IP addresswriting step).

(e) The controller 4 then detects a signal (referred to below as theDHCP setup signal) indicating whether DHCP should be used (S18: DHCPsetup signal detection step).

(f) If the DHCP setup signal is detected in the DHCP setup signaldetection step S18, a flag indicating using the DHCP function of therouter 103 is set and written to working memory 5 and nonvolatile memory6 (S19: dynamic IP setup step).

By forming a loop returning to before the static IP address detectionstep S16 after the static IP address writing step S17, DHCP setup signaldetection step S18, and dynamic IP setup step S19, the system waits forthe static IP address signal and DHCP setup signal. The LAN adapter 100can thus be used on the LAN.

Even if the user connects a LAN adapter 100 to a LAN and attempts toinitialize the IP address of the LAN adapter 100 while the LAN adapter100 can communicate with other devices on the network, the IP addresswill not be initialized with this first embodiment of the invention ifit is confirmed in the connection detection step S6 that there is adevice on the LAN connected to the LAN adapter 100. More specifically,the connection detector 14 detects information from the management unit3 relating to the connection of the LAN adapter 100 on the LAN, andconfirms that there is a connection by communicating with the LANadapter 100 over the LAN. If there is a connected device, the IP addressinitialization unit 15 initializes the working memory 5 and then writesthe content of nonvolatile memory 6 to working memory 5, and the IPaddress is not initialized. In other words, the IP address of the LANadapter 100 is not changed. As a result, problems with the LANcommunication system including LAN adapter 100 that can occur when theIP address of the LAN adapter 100 is changed while the LAN adapter 100is communicating with another device can be prevented.

(Embodiment 2)

FIG. 9 is a block diagram of the configuration of a LAN adapter 100according to a second embodiment of the present invention. This LANadapter 100 differs from the LAN adapter of the first embodiment in thata reset means composed of reset button 9, reset unit 10, and powersupply 11 is connected to the connection detector 14 instead of an IPaddress initialization button. This LAN adapter combines the resetbutton 9 and IP address initialization button 13. This simplifiesconstruction of the LAN adapter, enables IP address initialization bystarting the power supply, and improves operability for the user.

FIG. 10 is a flow chart of a method for initializing the IP address ofthis LAN adapter 100. This is a method for configuring the communicationparameters when the user does not know the current IP address of the LANadapter 100 stored in nonvolatile memory 6. This IP addressinitialization method has the following steps.

(a) The reset operation is started by the user pressing the reset button9 or starting to supply power to the power supply 11 (S21: reset step).

(b) The connection detector 14 detects whether there is a device on theLAN connected to the LAN adapter 100 (S22: connection detection step).

(c) If the connection detector 14 determines that there is no device onthe LAN connected to the LAN adapter 100 (yes), working memory 5 iscleared by the controller 4 (S23: working memory initialization step).

(d) After the working memory 5 is initialized, the default IP addressstored in ROM 7 is written to nonvolatile memory 6, and the content of.nonvolatile memory 6 is then written to working memory 5 (S24: defaultIP address writing step). This “default IP address” means the IP addressstored in ROM 7. Writing this default IP address to working memory 5enables the known IP address of the LAN adapter 100 to be used whensetting the communication parameters. It should be noted that the firststorage device comprises working memory 5 and nonvolatile memory 6.

(e) If the connection detector 14 determines that there is a device onthe LAN connected to LAN adapter 100 (no), working memory 5 is clearedby controller 4 (S25: working memory initialization step).

(f) After initializing the working memory 5, the content of nonvolatilememory 6 is written to working memory 5 (S26: write content ofnonvolatile memory step). The IP address of the LAN adapter 100 is notinitialized in this case. If the IP address is changed when there isalready a device on the LAN connected to the LAN adapter 100, the LANadapter 100 will no longer be recognized by that device. This problemcan be prevented, however, by writing the current IP address whenanother device is known to be connected to the LAN adapter 100.

As described in the first embodiment, the LAN adapter 100 according tothis second embodiment can be an information appliance 101 having theLAN adapter 100 as one component thereof. Incorporating the LAN adapter100 inside the information appliance 101 makes handling the LAN adapter100 easier than when it is a separate device.

In the first and second embodiments described above the first storagedevice includes both the working memory 5 and nonvolatile memory 6, butthe invention shall not be so limited and the first storage device couldhave only nonvolatile memory 6. That is, the IP address stored innonvolatile memory 6 could be used directly as the IP address of the LANadapter 100. This configuration makes the working memory 5 unnecessary,and further simplifies construction of the LAN adapter 100.

Furthermore, ROM 7 is used as the second storage device in the first andsecond embodiments described above, but the invention shall not be solimited and it could be flash memory or other nonvolatile memory device.More specifically, the second storage device can be any storage devicecapable of retaining the stored content when LAN adapter 100 power isoff.

Furthermore, one LAN adapter and data processing device each areconnected in addition to the router 103 to the LAN in the above firstand second embodiments of the invention, but multiple LAN adapters anddata processing devices could be connected to the LAN.

A LAN adapter according to the present invention thus described can thusreset the IP address of the LAN adapter to a default IP address known tothe user and thereby restore the LAN connection even when the user orrouter does not know the currently set IP address.

Although the present invention has been described in connection with thepreferred embodiments thereof with reference to the accompanyingdrawings, it is to be noted that various changes and modifications willbe apparent to those skilled in the art. Such changes and modificationsare to be understood as included within the scope of the presentinvention as defined by the appended claims, unless they departtherefrom.

1. A LAN adapter for connecting an information appliance to a local areanetwork, comprising: a first storage device which stores a currentlyrecognized IP address of the LAN adapter on the LAN; a second storagedevice which stores a default IP address for the LAN adapter; an IPaddress initialization controller which controls initializing the IPaddress of the LAN adapter; a connection detector which detects whetherthere is a device on the LAN connected to the LAN adapter in response toa command from the IP address initialization controller; an IP addressinitialization means which initializes the IP address of the LAN adapteraccording to the connection detected by the connection detector; and acontroller which writes the default IP address stored in the secondstorage device to the first storage device as the IP address of the LANadapter, when the connection detector determines that there is no deviceon the LAN connected to the LAN adapter, and which controls the firststorage device and second storage device.
 2. A LAN adapter according toclaim 1, wherein the first storage device comprises working memory andnonvolatile memory, and when the connection detector determines thatthere is no device on the LAN connected to the LAN adapter, thecontroller initializes the working memory, and writes the default IPaddress stored in the second storage device to nonvolatile memory as theIP address of the LAN adapter, then the controller writes the content ofthe nonvolatile memory to the working memory.
 3. A LAN adapter accordingto claim 1, wherein the first storage device comprises working memoryand nonvolatile memory, and when the connection detector determines thatthere is a device on the LAN connected to the LAN adapter, thecontroller initializes the working memory, and writes the content of thenonvolatile memory to the working memory.
 4. A LAN adapter according toclaim 3, wherein the LAN adapter further comprises a reset means, andwhen the reset means is operated initializes the working memory, andwrites the content of the nonvolatile memory to working memory.
 5. A LANadapter according to claim 1, wherein the second storage device is ROM.6. A LAN adapter according to claim 1, wherein the LAN adapter furthercomprises: a LAN port for connecting the LAN adapter to a LAN;management means which acquires and managing LAN information through theLAN port; and input/output means which connects the LAN adapter to theinformation appliance.
 7. An information appliance connected to a localarea network, comprising: a first storage device which stores acurrently recognized IP address of the information appliance on the LAN;a second storage device which stores a default IP address for theinformation appliance; an IP address initialization controller whichcontrols initializing the IP address of the information appliance; aconnection detector which detects whether there is a device on the LANconnected to the information appliance in response to a command from theIP address initialization controller; an IP address initialization meanswhich initializes the IP address of the information appliance accordingto the connection detected by the connection detector; and a controllerwhich writes the default IP address stored in the second storage deviceto the first storage device as the IP address of the informationappliance, when the connection detector determines that there is nodevice on the LAN connected to the information appliance, and whichcontrols the first storage device and second storage device.
 8. A methodfor initializing the IP address of a LAN adapter connecting aninformation appliance to a LAN, comprising the steps of: commandinginitializing the IP address of the LAN adapter; determining in responseto said command if there is a device connected to the LAN adapter on theLAN; and writing the default IP address stored in a second storagedevice to a first storage device as the IP address of the LAN adapterwhen it is determined that there is no device connected to the LANadapter.